This application claims the priority of German application 198 09 636.4, filed Mar. 6, 1998 in Germany, the disclosure of which is (are) expressly incorporated by reference herein.
The present invention relates to an opening device for an open-end spinning aggregate comprising a housing which takes up an opening roller, which housing comprises a base plate arranged perpendicular to the axis of the opening roller, which base plate is provided with a sheet metal insert having an anti-adhesive coating.
In spite of the cotton being cleaned when the sliver is made, the fibers to be spun in the open-end spinning aggregate can still contain impurities in the form of "honeydew". Honeydew is composed of sticky insect deposits, as well as plant nectar secretions, which fall on the cotton. Honeydew makes the fibers stick together and makes opening in the opening device difficult. The sticky deposits are deposited on those parts of the opening device where either the fiber material slides along guiding surfaces or where impurities from the opening device are ejected in a trash removal opening.
In order to avoid honeydew deposits, it is disclosed in U.S. Pat. No. 5,398,494 that the peripheral surfaces of the opening roller which come into contact with the fibers as well as the defining walls of a trash removal opening are directly provided with an anti-adhesive coating. This coating can be provided on a base plate which is arranged perpendicular to an axis of the opening roller in the area of the trash removal opening. In this publication it is additionally disclosed that the trash removal opening can be in the form of a shaft-like insert part made of sheet metal, which comprises the anti-adhesive coating.
Anti-adhesive coatings applied directly to the base plate are not possible if the coating has to be hardened by means of heat treatment, and the housing is not sufficiently heat resistant, for example, when it is made from a zinc casting.
It is an object of the present invention, in the case of antiadhesive coatings of housings of opening devices, not to have to take the material of the housing into consideration and, in relation to the surfaces of the base plate to be coated, not to be restricted to the area of a trash removal opening.
This object has been achieved in accordance with the present invention in that the metal insert is a flat sheet of metal which covers the base plate.
With the application of the present invention it is possible, while retaining the current design, to provide the base plate of the housing of the opening device with an anti-adhesive coating. Only a very slight change in the tolerance of the housing need be undertaken for the metal sheet which measures only a few tenths of a millimeter. The metal sheet can be made from a material which fulfills the specifications of the anti-adhesive coating. Thus the material of the base plate is, for the purpose of the present invention, irrelevant. In addition, it is now possible to render the entire base plate and not only the area of a trash removal opening insensitive to honeydew deposits.
In an embodiment of the present invention, the sheet metal can be clamped to the base plate by means of the peripheral walls surrounding the opening roller. It is then not necessary to adhere the metal sheet to the base plate or otherwise affix it thereto. As the peripheral walls have, in any case, to be affixed to the base body, the metal sheet can be a thin washer between the base plate and the peripheral walls.
When the anti-adhesive coating is applied to the metal sheet in conjunction with heat treatment, the thin metal sheet becomes somewhat convex on the coating side, that is, the metal sheet curves slightly. This can be used to advantage in that the metal sheet in an unclamped state is slightly curved in such a way that it is disposed only with its edge areas on the base plate. After the metal sheet has been clamped to the base plate by the peripheral walls, the metal sheet is disposed flat on the base plate.
The metal sheet is provided for the purpose of the present invention from the start with recesses for the opening roller and for a feed roller arranged upstream of the opening roller. The opening roller and the feed roller penetrate the metal sheet, which thus covers all surfaces on the base plate of the opening device, whereby the anti-adhesive coating of the metal sheet effectively prevents the depositing of honeydew.
As mentioned above, the metal sheet can be made more heat resistant than the base plate. For example, the base plate can be made of zinc casting, whereby the metal sheet can be made of coated aluminum or steel.
A ceramic layer has proved to be suitable as an anti-adhesive coating for the metal sheet, which ceramic layer is shot through with polytetrafluor ethylene (PTFE). The ceramic layer is applied to the metal sheet on one side by means of a hot plasma jet, during which the metal sheet is deformed to a slight convex shape. The ceramic layer is subsequently sprayed with PTFE, whereby this plastic penetrates to the base plate and into the ceramic pores of the metal sheet. Hardening then takes place by means of heat treatment at approximately 350.degree. C. The coating, a mixture of ceramic and PTFE, provides not only a very good wear resistance due to its scratch-resistance, but has such a low friction coefficient that it is suitable as an anti-adhesive coating against trash und in particular against honeydew.